Infrared fluorescent coatings

ABSTRACT

A coating composition includes: (i) a film-forming resin; (ii) an infrared reflective pigment; and (iii) an infrared fluorescent pigment or dye different from the infrared reflective pigment. A multi-layer coating including the coating composition, and a substrate at least partially coated with the coating composition is also disclosed. A method of detecting an article at least partially coated with the coating composition is also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/067,537, which is a national stage entry ofInternational Patent Application No. PCT/US2016/059336, filed Oct. 28,2016, which claims priority to U.S. Provisional Application Ser. No.62/272,391 filed Dec. 29, 2015, U.S. Provisional Application Ser. No.62/272,357 filed Dec. 29, 2015, and U.S. Provisional Application Ser.No. 62/272,377 filed Dec. 29, 2015, the disclosures of which are eachhereby incorporated by reference in their entireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with Government support under Contract No.DE-EE-0006347 awarded by the U.S. Department of Energy. This inventionwas made with Government support under Contract No. DE-AC02-05CH11231awarded by the U.S. Department of Energy. The United States Governmentmay have certain rights in this invention.

FIELD OF THE INVENTION

The present invention relates to a coating composition including a filmforming resin, an infrared reflective pigment, and an infraredfluorescent pigment or dye different from the infrared reflectivepigment. The present invention also relates to a multi-layer coatingcomposition, a coated substrate, and a method of detecting an article.

BACKGROUND OF THE INVENTION

With recent advances in technologies related to autonomous vehicles, itis becoming increasingly important that the vehicles and other objectsin a vehicle's surroundings include markings or coatings that aredetectable by a sensor mounted on another vehicle. This allows vehicleshaving the sensor to determine the proximity of the coated vehicle orobject and take the necessary course of action, such as braking,accelerating, swerving, or other maneuver, without human intervention.Therefore, there is an increasing need for coating applications relatingto autonomous vehicle guidance.

Infrared (IR) absorbance by a coating may lower contrast in a sensorradiation range and may make detection difficult. Coatings with improvedIR reflection may improve the sensor contrast. However, this approach islimited to the intensity of the IR wavelengths in the radiation sourceemployed. Thus, coatings capable of producing a detectable signal thatcan be recognized by sensors even when radiation sources are lessintense are desirable.

SUMMARY OF THE INVENTION

The present invention is directed to a coating composition including:(i) a film-forming resin; (ii) an infrared reflective pigment; and (iii)an infrared fluorescent pigment or dye different from the infraredreflective pigment.

The present invention is also directed to a multi-layer coatingincluding: (i) a first coating layer comprising a cured infraredreflective coating composition; and (ii) a second coating layeroverlying at least a portion of the first coating layer. The secondcoating layer includes a cured coating composition including: (a) afilm-forming resin; (b) an infrared reflective pigment; and (c) aninfrared fluorescent pigment or dye different from the infraredreflective pigment.

The present invention is also directed to a substrate at least partiallycoated with a coating composition including: (i) a film-forming resin;(ii) an infrared reflective pigment; and (iii) an infrared fluorescentpigment or dye different from the infrared reflective pigment.

The present invention is also directed to a method of detecting anarticle including: (a) exposing a surface of an article to radiationcomprising fluorescence-exciting radiation, the surface being at leastpartially coated with a coating composition including: (i) afilm-forming resin, (ii) an infrared reflective pigment, and (iii) aninfrared fluorescent pigment or dye different from the infraredreflective pigment; and (b) detecting fluorescence emitted by the coatedsurface in the infrared spectrum.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the X-ray diffraction (XRD) patterns of Al₂O₃doped with 1 wt % Cr₂O₃ and 3 wt % of Cr₂O₃;

FIG. 2 shows micrographs of two different Al₂O₃:Cr pigments obtained byscanning electron microscopy (SEM);

FIG. 3 shows a plot of the surface temperatures versus time ofcalibration panels;

FIG. 4 shows a fluorescence spectra for 3 wt % Cr₂O₃ doped Al₂O₃pigments excited at 500 nm;

FIG. 5 shows a fluorescence spectra for Egyptian blue pigments excitedat 600 nm;

FIGS. 6A and 6B are graphs showing fluorescence spectra ofhighly-pigmented coatings with 500 g/m² of 0 to 3 wt % Cr₂O₃ doped Al₂O₃obtained with NIR spectrofluorometers;

FIG. 7 is a graph showing the fluorescence spectra for a) an Egyptianblue pigment, b) a 0.14 P:B Egyptian blue coating over chrome primedaluminum substrate and c) a 0.4 P:B Egyptian blue coating over a chromeprimed aluminum substrate;

FIG. 8 is a graph of NIR fluorescence spectra for a) Egyptian blue andb) Han purple coatings over a white substrate;

FIG. 9 is a graph showing reflectance of Cd pigments in acrylic-basedartists paints over a white substrate;

FIG. 10 shows a graph of reflectance of 3 cadmium pigments (dark red,medium red, and light red) and a zirconia red pigment;

FIG. 11 shows a graph of spectral reflectance of smalt blue (CoO·K·Si)as compared to the spectral reflectance of Egyptian blue (CaCuSi₄O₁₀);

FIG. 12 shows NIR fluorescence spectra of several alkali earth coppersilicates;

FIG. 13 shows plots of spectral reflectance for PVDF-type coatingscontaining Ba(La,Li)CuSi₄O₁₀ (small particles) and SrCuSi₄O₁₀ (largeparticles) over white and yellow substrates;

FIG. 14 shows plots of spectral reflectance for acrylic-type coatingscontaining Ba(La,Li)CuSi₄O₁₀ (small particles) and SrCuSi₄O₁₀ (largeparticles) over white and yellow substrates;

FIG. 15 shows reflectance of the yellow primer and the white-coatedsubstrates used in the coatings of FIGS. 14 and 15 ;

FIG. 16A shows fluorescence from several samples made with SrCuSi₄O₁₀(large particle size); FIG. 16B shows plots similar to those of FIG.16A, but utilizing the Ba(La,Li)CuSi₄O₁₀ (small particle size); FIG. 16Cshows reflectance data that corresponds to FIGS. 16A and 16B; FIG. 16Dshows fluorescence of a strontium compound doped with equal amounts ofLa and Li, compared with an undoped material; FIG. 16E shows reflectancedata corresponding to FIG. 16D; FIG. 16F shows fluorescence data on aBaCuSi₄O₁₀ sample that is contaminated with CuO; FIG. 16G showsreflectance data corresponding to the prior fluorescence plot; FIG. 16Hshows fluorescence of Egyptian blue samples; FIG. 16I shows reflectancedata corresponding to FIG. 16H;

FIG. 17 shows nine NIR fluorescence spectra corresponding to coatingscontaining 1.5 wt % Cr₂O₃ doped Al₂O₃ in PVDF-based coatings at threeP:B ratios (0.2, 0.4, and 0.8) and three film thicknesses (1 coat, 2coats, 3 coats) per P:B ratio;

FIG. 18 shows temperature measurements for 18 test samples and 4calibrated reference samples;

FIG. 19 shows NIR fluorescence spectra for PVDF-based coatingscontaining Sr(La,Li)CuSi₄O₁₀ at P:B ratios of 0.2, 0.4 and 0.8 appliedover aluminum substrates coated with a yellow chrome primer and whiteprimer with film thicknesses for each P:B coating of 0.8 mils, 1.6 milsand 2.4 mils;

FIG. 20 shows peak heights of the coatings of FIG. 19 as a function ofthe product of P:B ratio and coating thickness;

FIG. 21 shows A) substrates coated with dark brown PVDF-based coatingswith varying weight percentages of ruby pigment and B) substrates coatedwith black PVDF-based coatings with varying weight percentages of HanBlue pigment;

FIG. 22 shows coatings including Sr(La,Li)CuSi₄O₁₀ (Top),Sr(La,Li)CuSi₄O₁₀ with azo yellow (Bottom left) and Sr(La,Li)CuSi₄O₁₀with Shepherd yellow 193 (Bottom right);

FIG. 23 shows a photograph of a blue-shade black sample made with aSrCuSi₄O₁₀ (large) pigmented acrylic coating over orange over a brightwhite substrate;

FIG. 24 shows Left: a coating containing NIR fluorescent pigment (Hanblue pigment) and IR reflective pigment (Shepherd 10C341)—Right: acoating containing IR reflective pigment (Shepherd 10C341);

FIG. 25 shows NIR fluorescence spectra of a coating containing NIRfluorescent blue/IR reflective orange and a coating containing IRreflective pigments; and

FIG. 26 shows a plot of thermal measurements conducted on severalcoatings containing varying levels of NIR fluorescent ruby pigment.

DESCRIPTION OF THE INVENTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities ofingredients used in the specification and claims are to be understood asbeing modified in all instances by the term “about”. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Inaddition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances. Further, in this application, the use of “a”or “an” means “at least one” unless specifically stated otherwise. Forexample, “a” pigment, “a” film-forming resin, “an” inorganic oxide, andthe like refer to one or more of any of these items. Also, as usedherein, the term “polymer” is meant to refer to prepolymers, oligomersand both homopolymers and copolymers. The term “resin” is usedinterchangeably with “polymer.” The term “metal” includes metals, metaloxides, and metalloids.

As used herein “wavelength” includes a spectral range of wavelengths,such as a spectral peak having a 25 nm, 50 nm, 75 nm, 100 nm, 125 nm,200 nm range on both sides of the spectral peak. As such, “wavelength”may refer to a spectral range of wavelengths encompassing up to 50 nm,up to 100 nm, up to 150 nm, up to 200 nm, up to 250 nm, up to 400 nm.

The present invention is directed to a coating composition including afilm-forming resin, an infrared (“IR”) reflective pigment, and an IRfluorescent pigment or dye different from the IR reflective pigment. Thecoating composition, when cured to form a coating and exposed tofluorescence-exciting radiation, may emit fluorescence in the IRspectrum at a greater intensity compared to the same coating exposed tothe fluorescence-exciting radiation except without the IR fluorescentpigment or dye. The coating composition, when cured to form a coatingand exposed to fluorescence-exciting radiation, may emit fluorescence inthe IR spectrum at least twice, such as at least 3 times, at least 5times, at least 7 times, at least 9 times, at least 10 times, at least25 times, at least 50 times the intensity compared to the same coatingexposed to the fluorescence exciting radiation except without the IRfluorescent pigment or dye.

IR Reflective Pigment

The coatings according to the present invention may include one or moreIR reflective pigments. As used herein, the term “IR reflective pigment”refers to a pigment that, when included in a curable coatingcomposition, provides a cured coating that reflects IR radiation, suchas NIR radiation, greater than a cured coating deposited in the samemanner from the same composition but without the IR reflective pigment.As used herein, IR radiation refers to radiation energy having awavelength ranging from 700 nanometers to 1 millimeter. NIR radiationrefers to radiation energy having a wavelength ranging from 700 to 2500nanometers. The IR reflective pigment may reflect environmental IRradiation as well as radiation produced by the IR fluorescent pigment ordye described below. The coating may comprise the IR reflective pigmentin an amount sufficient to provide a cured coating that has a solarreflectance, measured according to ASTM E903-96 in the wavelength rangeof 700-2500 nm, that is at least 2, or at least 5 percentage pointshigher than a cured coating deposited in the same manner from the samecoating composition in which the IR reflective pigment is not present.Non-limiting examples of IR reflective pigments include inorganic ororganic materials. Non-limiting examples of suitable IR reflectivepigments include any of a variety of metals and metal alloys, inorganicoxides, and interference pigments. Non-limiting examples of IRreflective pigments include titanium dioxide, titanium dioxide coatedmica flakes, iron titanium brown spinel, chromium oxide green, ironoxide red, chrome titanate yellow, nickel titanate yellow, blue andviolet. Suitable metals and metal alloys include aluminum, chromium,cobalt, iron, copper, manganese, nickel, silver, gold, iron, tin, zinc,bronze, brass, including alloys thereof, such as zinc-copper alloys,zinc-tin alloys, and zinc-aluminum alloys, among others. Some specificnon-limiting examples include nickel antimony titanium, nickel niobiumtitanium, chrome antimony titanium, chrome niobium, chrome tungstentitanium, chrome iron nickel, chromium iron oxide, chromium oxide,chrome titanate, manganese antimony titanium, manganese ferrite,chromium green-black, cobalt titanates, chromites, or phosphates, cobaltmagnesium and aluminites, iron oxide, iron cobalt ferrite, irontitanium, zinc ferrite, zinc iron chromite, copper chromite, as well ascombinations thereof.

More particularly, commercially available non-limiting examples of IRreflective pigments include RTZ Orange 10C341 (rutile tin zinc), Orange30C342, NTP Yellow 10C151 (niobium tin pyrochlore), Azo Yellow, Yellow10C112, Yellow 10C242, Yellow 10C272, Yellow 193 (chrome antimonytitanium), Yellow 30C119, Yellow 30C152, Yellow 30C236, Arctic Black10C909 (chromium green-black), Black 30C933, Black 30C941, Black 30C940,Black 30C965, Black 411 (chromium iron oxide), Black 430, Black 20C920,Black 444, Black 10C909A, Black 411A, Brown 30C888, Brown 20C819, Brown157, Brown 10C873, Brown 12 (zinc iron chromite), Brown 8 (iron titaniumbrown spinel), Violet 11, Violet 92, Blue 30C588, Blue 30C591, Blue30C527, Blue 385, Blue 424, Blue 211, Green 260, Green 223, Green 187B,Green 410, Green 30C612, Green 30C6054, Green 30C678, and mixturesthereof. The IR reflective pigments can be added to the coatingcomposition in any suitable form, such as discrete particles,dispersions, solutions, and/or flakes.

The IR reflective pigments can also be incorporated into the coatingcomposition in any suitable form, e.g., by use of a grind vehicle, suchas an acrylic grind vehicle, the use of which will be familiar to oneskilled in the art. The IR reflective pigments, if they do not absorbthe IR fluorescence emission, can be used to adjust the visible color ofthe coating.

IR Fluorescent Pigment or Dye

As previously mentioned, the coating composition of the presentinvention includes at least one IR fluorescent pigment or dye. As usedherein, the term “IR fluorescent pigment or dye” refers to a pigment ordye which fluoresces in the IR region (700 nm-1 mm) of theelectromagnetic spectrum. The IR fluorescent pigment or dye mayfluoresce in the NIR region (700-2500 nm) of the electromagneticspectrum. The IR fluorescent pigment or dye may be an organic orinorganic pigment or dye. The IR fluorescent pigment or dye mayfluoresce at a lower energy wavelength when excited by a higher energywavelength. For instance, the IR fluorescent pigment or dye mayfluoresce in the 700-1500 nm region (a comparatively lower energywavelength) when excited by radiation in the 300-700 nm region (acomparatively higher energy wavelength).

Non-limiting examples of suitable IR fluorescent pigments includemetallic pigments, metal oxides, mixed metal oxides, metal sulfides,metal selenides, metal tellurides, metal silicates, inorganic oxides,inorganic silicates, alkaline earth metal silicates. As used herein, theterm “alkaline” refers to the elements of group II of the periodic tableBe, Mg, Ca, Sr, Ba, and Ra (beryllium, magnesium, calcium, strontium,barium, radium). Non-limiting examples of suitable IR fluorescentpigments include metal compounds, which may be doped with one or moremetals, metal oxides, alkali and/or rare earth elements. As used herein,the term “alkali” refers to the elements of group I of the periodictable Li, Na, K, Rb, Cs, and Fr (lithium, sodium, potassium, rubidium,cesium, francium). As used herein, the term “rare earth element” refersto the lanthanide series of elements La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,Dy, Ho, Er, Tm and Yb (lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium).

Non-limiting examples of IR fluorescent pigments include Egyptian blue(CaCuSi₄O₁₀), Han blue (BaCuSi₄O₁₀), Han purple (BaCuSi₂O₆), SrCuSi₄O₁₀,ruby (Al₂O₃:Cr), Sr(La, Li)CuSi₄O₁₀, and Ba(La, Li)CuSi₄O₁₀. Inparticular, blue alkali earth copper silicates, such as Egyptian blue(CaCuSi₄O₁₀) fluoresce in the 800 to 1200 nm region. Cadmium pigments,CdSe and CdTe compounds, “zirconia” red (red cadmium pigments coatedwith a zirconium silicate glass), indigo, blue verditer(2CuCO₃·Cu(OH)₂), copper blue, azurite (Cu₃(CO₃)₂(OH)₂), Ploss blue((CuCa)(CH₃COO)₂·2H₂O), and smalt (CoO·K·Si) may possess weakfluorescence.

Other non-limiting examples of IR fluorescent pigments may include ZnO,ZnS, ZnSe, ZnTe, (Zn(O,S,Se,Te). These IR fluorescent pigments haveenergy gaps that are too large for band-to-band emission of IR energy,but doping with Sn, Mn, and Te can lead to suitable impurityluminescence. Other non-limiting examples of IR fluorescent pigments mayinclude compounds used in lighting and for fluorescent displays; certaindirect bandgap semiconductors, such as (Al,Ga)As, InP, and the like; andmaterials used for solid state lasers, such as Nd doped yttrium aluminumgarnet, and titanium doped sapphire. In addition, non-limiting examplesof IR fluorescent pigments may include phosphors that emit in the deepred or IR (e.g, LiAlO₂:Fe, CaS:Yb).

As previously mentioned, the IR fluorescent pigment or dye may beorganic or inorganic. Non-limiting examples of suitable IR fluorescentorganic pigments and/or dyes include rhodamines,spiro[indeno[1,2-b]chromene-10,1′-isobenzofuran]-3′-ones,7-(dialkylamino)-3′H,11H-spiro[indeno[1,2-b]chromene-10,1′-isobenzofuran]-3′-ones,changsha (CS1-6) NIR fluorophores, thienopyrazines,aminobenzofuran-fused rhodamine dyes (AFR dyes) containing amino groups,sulforhodamine dyes, perylenediimide to hexarylenediimides,donor-acceptor charge transfer compounds such as substitutes thiophenes,diphenylbenzobisthiadiazoles, and selenium or tellurium substitutedderivatives, cyclic polyenes, cyclic polyene-ynes, perylenes,perylenebis(dicarboximide)s such as perylene bis(phenethylimide, orperylene bis(2,5-di-tert-butylphenylimide), perylene diimides containingnitrogen donor groups, polymethines, borondipyrromethenes,pyrrolopyrrole cyanines, squaraine dyes, tetrathiafulvalene, thiadiazolefused chromophores, phthalocyanine and porphyrin derivatives,metalloporphyrins, BODIPY (borondipyrromethane) dyes, tricarbocyanines,rubrenes, and carbon nanotubes.

The IR fluorescent organic pigment and/or dye can be encapsulated asnanoparticles in polymers such as an amphiphilic block copolymer. Forexample, an amphiphilic block copolymer encapsulating IR fluorescentorganic pigment and/or dye nanoparticles comprisespoly(caprolactone)-b-poly-(ethylene glycol) (PCL-b-PEG). Furthermore,the at least one IR fluorescent organic pigment and/or dye can becovalently bonded to the polymer matrix of the encapsulating polymer. Inaddition, the IR fluorescent organic pigment and/or dye can be anchoredto a polymeric or inorganic particle.

The IR fluorescent pigments or dyes can be added to the coatingcomposition used to prepare the coatings in any suitable form, such asdiscrete particles, dispersions, solutions, and/or flakes. The IRfluorescent pigments or dyes can also be incorporated into the coatingsby use of a grind vehicle, such as an acrylic grind vehicle, the use ofwhich will be familiar to one skilled in the art.

The IR fluorescent pigments or dyes can be used as additives in coatingcompositions to provide coatings producing IR fluorescent emissiveand/or absorptive responses that are capable of being detected by asensor. The fluorescence emitted by the IR fluorescent pigment or dyemay be detectable by the sensor. The sensor may include a sensitivity inthe IR region of the electromagnetic spectrum. The sensor may be an IRspectrofluorometer. The sensor may be an image sensor (an array ofphotodiodes) or a single photodiode.

IR Transparent Pigment

The coating composition may also optionally include at least one IRtransparent pigment. As used herein, an “IR transparent pigment” refersto a pigment that is substantially transparent (having the property oftransmitting energy, e.g. radiation, without appreciable scattering inthose wavelengths) in the IR wavelength region (700 nm-1 mm), such as inthe NIR wavelength region (700 to 2500 nanometers), such as is describedin United States Patent Application Publication No. 2004/0191540 at[0020]-[0026], United States Patent Application Publication No.2010/0047620 at [0039], United States Patent Application Publication No.2012/0308724 at [0020]-[0027], the cited portions of which beingincorporated herein by reference. The IR transparent pigment may have anaverage transmission of at least 70% in the IR wavelength region. The atleast one IR transparent pigment can be used to adjust the visible colorof the coating composition, i.e., may be a colorant. The IR transparentpigment may not be transparent at all wavelengths in the IR range butshould be largely transparent in the fluorescent emission wavelength ofthe IR fluorescent pigment or dye.

The IR reflective pigment may reflect radiation at a first wavelengthwhen exposed to radiation comprising fluorescence-exciting radiation andthe IR fluorescent pigment or dye may fluoresce at a second wavelengthwhen exposed to radiation comprising fluorescence-exciting radiation.The balance of the coating composition (i.e. the remaining components ofthe coating composition excluding the IR reflective pigment and the IRfluorescent pigment or dye) may be transparent at the first and secondwavelengths so as not to adversely affect IR reflection or IRfluorescence or not to affect the visible color of the coatingcomposition.

Film-Forming Resin

The present invention includes a film-forming resin including resinsbased on fluoropolymers (including poly(vinylidene fluoride), PVDF),polyolefins, polyester polymers, polysiloxanes, silicone modifiedpolyester polymers, acrylic polymers, acrylic latex polymers, vinylpolymers, epoxy based polymers, polyurethanes, polyureas, polyimides,polyamides, polyanhydrides, phenol/formaldehyde polymers, polyetherpolymers, copolymers thereof, and mixtures thereof.

As used herein, a “film-forming resin” refers to a resin that can form aself-supporting continuous film on at least a horizontal surface of asubstrate upon removal of any diluents or carriers present in thecomposition or upon curing at ambient or elevated temperature.Film-forming resins that may be used in the present invention include,without limitation, those used in automotive OEM coating compositions,automotive refinish coating compositions, industrial coatingcompositions, architectural coating compositions, coil coatingcompositions, packaging coating compositions, protective and marinecoating compositions, and aerospace coating compositions, among others.The film-forming resin can include any of a variety of thermoplasticand/or thermosetting film-forming resins known in the art. As usedherein, the term “thermosetting” refers to resins that “set”irreversibly upon curing or crosslinking, wherein the polymer chains ofthe polymeric components are joined together by covalent bonds. Thisproperty is usually associated with a cross-linking reaction of thecomposition constituents often induced, for example, by heat orradiation. Curing or crosslinking reactions also may be carried outunder ambient conditions or at low temperatures. Once cured orcrosslinked, a thermosetting resin will not melt upon the application ofheat and is insoluble in solvents. As noted, the film-forming resin canalso include a thermoplastic film-forming resin. As used herein, theterm “thermoplastic” refers to resins that include polymeric componentsthat are not joined by covalent bonds and thereby can undergo liquidflow upon heating and are soluble in solvents.

The coating composition(s) described herein can comprise any of avariety of thermoplastic and/or thermosetting compositions known in theart. The coating composition(s) may be water-based or solvent-basedliquid compositions, or, alternatively, in solid particulate form, i.e.,a powder coating.

Thermosetting coating compositions typically comprise a crosslinkingagent that may be selected from, for example, melamines,polyisocyanates, including blocked polyisocyanate, polyepoxides,beta-hydroxyalkylamides, polyacids, anhydrides, organometallicacid-functional materials, polyamines, polyamides, alkoxysilanes andmixtures of any of the foregoing.

In addition to or in lieu of the above-described crosslinking agents,the coating composition may comprises at least one film-forming resin.Thermosetting or curable coating compositions may comprise film-formingpolymers having functional groups that are reactive with thecrosslinking agent. The film-forming resin in the coating compositionsdescribed herein may be selected from any of a variety of polymerswell-known in the art. The film-forming resin can be selected from, forexample, fluoropolymers, polyolefins, polyester polymers, polysiloxanes,silicone modified polyester polymers, acrylic polymers, acrylic latexpolymers, vinyl polymers, epoxy based polymers, polyurethanes,polyureas, polyimides, polyamides, polyanhydrides, phenol/formaldehydepolymers, polyether polymers, copolymers thereof, and mixtures thereof.

Generally these polymers can be any polymers of these types made by anymethod known to those skilled in the art. Such polymers may be solventborne or water dispersible, emulsifiable, or of limited watersolubility. The functional groups on the film-forming resin may beselected from any of a variety of reactive functional groups including,for example, carboxylic acid groups, amine groups, epoxide groups,hydroxyl groups, alkoxy groups, acetoacetoxy groups, thiol groups,carbamate groups, amide groups, urea groups, isocyanate groups(including blocked isocyanate groups), mercaptan groups, andcombinations thereof. Appropriate mixtures of film-forming resins mayalso be used in the preparation of the coating compositions describedherein.

The film-forming resin can be water dispersible. As used herein, a“water dispersible” resin is a polymer or oligomer that is solubilized,partially solubilized and/or dispersed in some quantity of water with orwithout additional water soluble solvents. The solution can besubstantially 100 percent water. The solution can be 50 percent waterand 50 percent co-solvent, 60 percent water and 40 percent co-solvent,70 percent water and 30 percent co-solvent, 80 percent water and 20percent co-solvent, or 90 percent water and 10 percent co-solvent.Suitable co-solvents include, for example, glycol ethers, glycolether-esters, alcohols, ether alcohols, N-methyl pyrrolidone, phthalateplasticizers and/or mixtures thereof. In certain applications, it may bedesirable to limit the amount of co-solvent.

The film-forming resin can also be solvent dispersible. As used herein,a “solvent dispersible” resin is a polymer or oligomer that issolubilized, partially solubilized and/or dispersed in some quantity ofa solvent other than water. Suitable solvents include, but are notlimited to, aliphatic hydrocarbons, aromatic hydrocarbons, ketones,esters, glycols, ethers, ether esters, glycol ethers, glycol etheresters, alcohols, ether alcohols, phthalate plasticizers. Ketonesinclude isophorone, N-methyl pyrrolidone and/or suitable mixturesthereof. Phthalate plasticizers include phthalates esters such asdiethylhexyl phthalate, diisononyl phthalate, diisodecyl phthalate,dioctyl phthalate, and butyl benzyl phthalate. Appropriate mixtures offilm-forming resins may also be used in the preparation of the presentcoatings.

As described above, the film-forming resin includes a polymer or mixtureof polymers chosen so that the film-forming resin is substantially freeof or essentially free of or completely free of an IR absorbingcompound. By substantially free it is meant that a coating compositiondoes not absorb IR radiation at a level which detracts from and/orinterferes with the reflection of radiation from the IR reflectivepigment or the IR fluorescent pigment to the extent that theirrespective intensities are diminished to an undetectable level.

The coatings may be prepared by direct incorporation of the dry IRfluorescent pigments or dyes and/or the dry IR reflective pigments intothe coating.

The IR fluorescent pigments or dyes and/or the IR reflective pigmentsmay be incorporated into the coating composition via one or more pigmentdispersion. As used herein, “pigment dispersion” refers to a compositionof pigment in a grinding resin (which may be the same as or differentfrom the film-forming resin described earlier). The pigment dispersionmay, but does not necessarily need to, include a pigment dispersant. Thepigment dispersions containing pigment particles are often milled in ahigh energy mill in an organic solvent system, such as butyl acetate,using a grinding resin (such as a film-forming resin and/or a pigmentdispersant).

The grinding resin is often present in the pigment dispersion in anamount of at least 0.1 percent by weight, such as at least 0.5 percentby weight, or at least 1 percent by weight, based on the total weight ofthe dispersion. The grinding resin is also often present in the pigmentdispersion in an amount of less than 65 percent by weight, or less than40 percent by weight, based on the total weight of the dispersion. Theamount of grinding resin present in the pigment dispersion may rangebetween any combinations of these values, inclusive of the recitedvalues.

The film-forming resin can comprise at least 0.05 weight %, at least 0.1weight %, at least 0.5 weight %, or at least 1 weight %, based on thetotal solids weight of the composition. The film-forming resin cancomprise up to 90 weight %, up to 70 weight %, or up to 60 weight %,based on the total solids weight of the composition.

The IR fluorescent pigments or dyes can comprise at least 0.05 weight %,at least 0.1 weight %, at least 0.5 weight or at least 1 weight %, basedon the total solids weight of the composition. The IR fluorescentpigments or dyes can comprise up to 50 weight %, up to 40 weight %, orup to 30 weight %, based on the total solids weight of the composition.

The IR reflective pigments can comprise at least 0.05 weight %, at least0.1 weight %, at least 0.5 weight or at least 1 weight %, based on thetotal solids weight of the composition. The IR reflective pigments cancomprise up to 50 weight %, up to 40 weight %, or up to 30 weight %,based on the total solids weight of the composition.

The IR fluorescent pigments or dyes have an average particle size of nomore than 10 microns, no more than 1 micron, or no more than 750 nm. Inparticular, the IR fluorescent pigments or dyes may have an averageparticle size of from 50 nm to 10 microns. In particular, the IRfluorescent pigments or dyes may have an average particle size of from100 nm to 1 micron, such as from 500 nm to 750 nm. A dispersioncontaining the IR fluorescent pigments or dyes is substantially free ofpigments having an average particle size of more than 10 microns, nomore than 1 micron, or no more than 750 nm. By “substantially free” itis meant that no more than 10% by weight, such as no more than 5% byweight, or no more than 1% by weight, of the IR fluorescent pigments ordyes present in the dispersion have an average particle size of morethan 10 microns, no more than 1 micron, or no more than 750 nm.

The IR reflective pigments have an average particle size of no more than10 microns, no more than 1 micron, or no more than 750 nm. A dispersioncontaining the IR reflective pigments are substantially free of pigmentshaving an average particle size of more than 10 microns, no more than 1micron, or no more than 750 nm.

The coatings of the present invention exhibit one or more IR fluorescentemission responses that are detectable. The detectable IR fluorescentemissive responses result from fluorescence-exciting radiation producedby, for instance, sunlight, incandescent lights, fluorescent lights,xenon lights (HID lights in automobiles), lasers, LED lights, or acombination thereof. For example, excitation wavelengths in a range of250 nm to 1600 nm can provide IR fluorescent emission responses that canbe detected from the coatings of the present invention.

The present invention is further directed to methods for preparingcoatings comprising blending a first dispersion of the film-formingresin and a second dispersion comprising one or more IR fluorescentpigments or dyes and optionally one or more IR transparent pigments.Alternatively, the method may also comprise blending into the first andsecond dispersion blends a third dispersion comprising one or more IRreflective pigments and/or one or more IR transparent pigments.Alternatively, the method may also comprise blending into the first andsecond dispersion blends a third dispersion comprising one or more IRreflective pigments. The final dispersion blend may then be dried. Ifdesired, the dried blend can then undergo grinding. The drying andgrinding are as described above. Blending can be done by any means knownin the art, such as mixing with a low shear mixer or by shaking. One orboth dispersions can be automatically dispensed from a computerizeddispensing system. For example, to a first film-forming resin dispersioncan be added a second pigment dispersion, or a combination of secondpigment dispersion(s) and third pigment dispersion(s) to achieve thedesired color. The correct amount and type of second and third pigmentdispersion(s) to add to the film-forming resin dispersion can bedetermined, for example, by use of color matching and/or colorgenerating computer software known in the art.

The first dispersion of the film-forming resin may comprisefluoropolymers, polyolefins, polyester polymers, polysiloxanes, siliconemodified polyester polymers, acrylic polymers, acrylic latex polymers,vinyl polymers, epoxy based polymers, polyurethanes, polyureas,polyimides, polyamides, polyanhydrides, phenol/formaldehyde polymers,polyether polymers, copolymers thereof, and mixtures thereof.

The second dispersion comprising an IR fluorescent pigment or dye (andoptionally an IR reflective pigment and/or IR transparent pigment) cancomprise the same dispersible resin as the first dispersion, or adifferent dispersible resin. If different dispersible resins are used,they should be selected so as to be compatible both with each other.Both the first and second dispersions can be water based, or both can besolvent based, or one can be water based and one can be solvent based.“Water based” means that the dispersion includes a water dispersibleresin; “solvent based” means that the dispersion includes a solventdispersible resin. The water-based dispersion can include a limitedamount of water-soluble solvents to improve application and film formingperformance.

The third dispersion comprising an IR reflective pigment and/or IRtransparent pigment can comprise the same dispersible resin as the firstand/or second dispersion, or a different dispersible resin. If differentdispersible resins are used, they should be selected so as to becompatible both with each other, and with the film-forming resin. Thefirst, second, and third dispersions can be water based, or they can besolvent based, or one or two can be water based and one or two can besolvent based. “Solvent based” means that the dispersion includes asolvent dispersible resin.

The IR fluorescent pigment(s) or dye(s), IR reflective pigment(s),and/or IR transparent pigment(s) can be added to the dispersion(s) inthe same manner as the reactants that form a polymer in the film-formingresin. The amount of colorant in the dispersion can be any amount thatimparts the desired color, such as from 0.5 to 50 weight percent, basedon the total weight of the reactants.

As described above, any of the dispersions can be water-based.Similarly, the medium of any of the dispersions can be substantially 100percent water, or can be 50 percent water and 50 percent co-solvent, 60percent water and 40 percent co-solvent, 70 percent water and 30 percentco-solvent, 80 percent water and 20 percent co-solvent, or 90 percentwater and 10 percent co-solvent, as described above.

It may be desired to partially or wholly neutralize any acidfunctionality on the film-forming resin. Neutralization can assist inthe preparation of a water based dispersion. Any suitable neutralizingagent can be used, such as triethyl amine, triethanol amine, dimethylethanolamine, methyl diethanolamine, diethyl ethanolamine, diisopropylamine, and/or ammonium hydroxide.

It may also be desirable to include a crosslinker in either or both ofthe dispersions. Any of the crosslinkers described above can be used.

It may be desirable to ensure that the proper spectral response and/orcolor for the coating is achieved. This can be done by doing, forexample, a drawdown or spray out of the blended dispersions to see ifthe appropriate spectral response and/or color is obtained. If not, moreof the pigment dispersion(s) or more of the film-forming resindispersion can be added to adjust the color accordingly. The adjustedblend can then be dried, or it can be further tested to confirm that thedesired color is achieved.

The coating composition may further include a colorant. The colorant mayinclude further pigments, dyes, tints, including but not limited tothose used in the paint industry and/or listed in the Dry ColorManufacturers Associate (DCMA) as well as special effect compositions. Acolorant may include, for example, a finely divided solid powder that isinsoluble but wettable under the conditions of use. A colorant may beorganic or inorganic and can be agglomerated or non-agglomerated. Thecolorant can be in the form of a dispersion including, but not limitedto, a nanoparticle dispersion. Nanoparticle dispersions can include oneor more highly dispersed nanoparticle colorants or colorant particlesthat produce a desirable visible color and/or opacity and/or visualeffect. Nanoparticle dispersions can include colorants such as pigmentsor dyes having a particle size less than about 150 nm, such as less than70 nm, or less than 30 nm.

Any additives standard in the coatings art can be added to any of thedispersions described above. This includes, for example, fillers,extenders, UV absorbers, light stabilizers, plasticizers, surfactants,wetting agents, defoamers and the like. In formulating the dispersionsdescribed above, it may also be desirable to add additional dispersibleresins the same as or compatible with that in which either of thepigment or film-forming resin polymer is dispersed in order to adjustthe level of film-forming resin polymer or pigment.

The coating composition may be substantially free of an IR absorbingcomponent. An IR absorbing component is one that absorbs radiation inthe IR region (700 nm-1 mm), such as in the NIR region (700-2500 nm).The coating composition may be completely free of an IR absorbingcomponent. As used herein, the term “substantially free”, when used inreference to an IR absorbing component, means that the IR absorbingcomponent is present in the composition in an amount no more than 0.1percent by weight, or no more than 0.05 percent by weight, based on thetotal solids weight of the composition. As used herein, the term“completely free”, when used in reference to an IR absorbing component,means the IR absorbing component is not present in the composition atall. The coating composition may include an IR absorbing component. TheIR absorbing component may absorb in the IR region but may not absorb atthe first wavelength (in which the IR reflective pigment reflects) or atthe second wavelength (in which the IR fluorescent pigment or dyefluoresces).

The present invention is also directed to a substrate at least partiallycoated with a coating prepared from the coating composition including atleast one IR fluorescent pigment or dye, IR reflective pigment, optionalIR transparent pigment, and film-forming resin based on fluoropolymers,polyolefins, polyester polymers, polysiloxanes, silicone modifiedpolyester polymers, acrylic polymers, acrylic latex polymers, vinylpolymers, epoxy based polymers, polyurethanes, polyureas, polyimides,polyamides, polyanhydrides, phenol/formaldehyde polymers, polyetherpolymers, copolymers thereof, and mixtures thereof. In non-limitingexamples, the coating composition can be applied to the substrate as atopcoat, a basecoat, or an undercoat. It should be understood that theuse of coatings containing IR fluorescent and IR reflective pigments mayrequire that any additional coatings applied on top of the coatingscontaining IR fluorescent and IR reflective pigments should absorb veryweakly in the IR, not absorb in the IR and/or if the coatings arecolored, contain IR transparent pigments.

The coating compositions described above are also suitable for use in,for example, multi-component composite coating systems, for example, asa primer coating or as a pigmented base coating composition in acolor-plus-clear system, or as a monocoat topcoat. The foregoing coatingcompositions can be used to form a topcoat in a multi-componentcomposite coating system that further comprises an IR reflective coatinglayer underlying at least a portion of the topcoat. As will beappreciated, various other coating layers may be present as previouslydescribed, such as, for example, a colorless clearcoat layer which maybe deposited over at least a portion of the topcoat. In addition, one ormore coating layers may be deposited between the topcoat and the IRreflective coating layer underlying the topcoat, optionally with thesecoating layers do not absorb in the IR. Moreover, one or more coatinglayers may be deposited between the substrate and the IR reflectivecoating layer underlying at least a portion of the topcoat, such as, forexample, various corrosion resisting primer layers, including, withoutlimitation, electrodeposited primer layers as are known in the art.

A multi-layer coating may include a first coating layer including acured IR reflective coating composition. A second coating layer mayoverlay at least a portion of the first coating layer, and the secondcoating layer may be the coating composition including the film-formingresin, IR reflective pigment, and IR fluorescent pigment or dye. Thefirst coating layer, being an IR reflective coating, may reflect thefluorescence exhibited by the IR fluorescent pigment or dye of thesecond coating layer away from the coated substrate.

The substrate upon which the coatings (e.g., the cured coatingcomposition or the multi-layer coating) described above may be depositedmay take numerous forms and be produced from a variety of materials. Thesubstrate may be at least a portion of an object in a vehicle'ssurroundings. Such objects may include another vehicle, a road, roadbarriers, signage, or other object that may be in the vehicle'ssurroundings. The substrate may take the form of (i) an automobilecomponent, such as an interior or exterior metal panel, leather orfabric seating areas, plastic components, such as dashboards or steeringwheels, and/or other interior vehicle surfaces; (ii) an aerospacecomponent, such as an aircraft exterior panel (which may be metal, suchas aluminum or an aluminum alloy, or produced from a polymeric compositematerial, for example), leather, plastic or fabric seating areas andinterior panels, including control panels and the like; (iii) a buildingcomponent, such as exterior panels and roofing materials; and (iv)industrial components, among others.

Suitable substrate materials include cellulosic-containing materials,including paper, paperboard, cardboard, plywood and pressed fiberboards, hardwood, softwood, wood veneer, particleboard, chipboard,oriented strand board, and fiberboard. Such materials may be madeentirely of wood, such as pine, oak, maple, mahogany, cherry, and thelike. The materials may comprise wood in combination with anothermaterial, such as a resinous material, i.e., wood/resin composites, suchas phenolic composites, composites of wood fibers and thermoplasticpolymers, and wood composites reinforced with cement, fibers, or plasticcladding. Suitable metallic substrate materials include, but are notlimited to, foils, sheets, or workpieces constructed of cold rolledsteel, stainless steel and steel surface-treated with any of zinc metal,zinc compounds and zinc alloys (including electrogalvanized steel,hot-dipped galvanized steel, GALVANNEAL steel, and steel plated withzinc alloy), copper, magnesium, and alloys thereof, aluminum alloys,zinc-aluminum alloys such as GALFAN™, GALVALUME™, aluminum plated steeland aluminum alloy plated steel substrates may also be used. Steelsubstrates (such as cold rolled steel or any of the steel substrateslisted above) coated with a weldable, zinc-rich or iron phosphide-richorganic coating are also suitable. Such weldable coating compositionsare disclosed in, for example, U.S. Pat. Nos. 4,157,924 and 4,186,036.Cold rolled steel is also suitable when pretreated with, for example, asolution selected from the group consisting of a metal phosphatesolution, an aqueous solution containing at least one Group IIIB or IVBmetal, an organophosphate solution, an organophosphonate solution, andcombinations thereof. Also, suitable metallic substrates include silver,gold, and alloys thereof.

Non-limiting examples of suitable silicon substrates are glass,porcelain and ceramics.

Non-limiting examples of suitable polymeric substrates are polystyrene,polyamides, polyesters, polyethylene, polypropylene, melamine resins,polyacrylates, polyacrylonitrile, polyurethanes, polycarbonates,polyvinyl chloride, polyvinyl alcohols, polyvinyl acetates,polyvinylpyrrolidones and corresponding copolymers and block copolymers,biodegradable polymers and natural polymers—such as gelatin.

Non-limiting examples of suitable textile substrates are fibers, yarns,threads, knits, wovens, nonwovens and garments composed of polyester,modified polyester, polyester blend fabrics, nylon, cotton, cotton blendfabrics, jute, flax, hemp and ramie, viscose, wool, silk, polyamide,polyamide blend fabrics, polyacrylonitrile, triacetate, acetate,polycarbonate, polypropylene, polyvinyl chloride, polyester microfibersand glass fiber fabric.

Non-limiting examples of suitable leather substrates are grain leather(e.g. nappa from sheep, goat or cow and box-leather from calf or cow),suede leather (e.g. velours from sheep, goat or calf and huntingleather), split velours (e.g. from cow or calf skin), buckskin and nubukleather; further also woolen skins and furs (e.g. fur-bearing suedeleather). The leather may have been tanned by any conventional tanningmethod, in particular vegetable, mineral, synthetic or combined tanned(e.g. chrome tanned, zirconyl tanned, aluminum tanned or semi-chrometanned). If desired, the leather may also be re-tanned; for re-tanningthere may be used any tanning agent conventionally employed forre-tanning, e.g. mineral, vegetable or synthetic taming agents, e.g.,chromium, zirconyl or aluminum derivatives, quebracho, chestnut ormimosa extracts, aromatic syntans, polyurethanes, (co) polymers of(meth)acrylic acid compounds or melamine, dicyanodiamide and/orurea/formaldehyde resins.

Non-limiting examples of suitable compressible substrates include foamsubstrates, polymeric bladders filled with liquid, polymeric bladdersfilled with air and/or gas, and/or polymeric bladders filled withplasma. As used herein the term “foam substrate” means a polymeric ornatural material that comprises an open cell foam and/or closed cellfoam. As used herein, the term “open cell foam” means that the foamcomprises a plurality of interconnected air chambers. As used herein,the term “closed cell foam” means that the foam comprises a series ofdiscrete closed pores. Non-limiting examples of foam substrates includepolystyrene foams, polymethacrylimide foams, polyvinylchloride foams,polyurethane foams, polypropylene foams, polyethylene foams, andpolyolefinic foams. Non-limiting examples of polyolefinic foams includepolypropylene foams, polyethylene foams and/or ethylene vinyl acetate(EVA) foam, EVA foam can include flat sheets or slabs or molded EVAforms, such as shoe midsoles. Different types of EVA foam can havedifferent types of surface porosity. Molded EVA can comprise a densesurface or “skin”, whereas flat sheets or slabs can exhibit a poroussurface.

The coating compositions of the present invention may be formulated andapplied using various techniques known in the art. The coatingcompositions from which each of the coatings described above isdeposited can be applied to a substrate by any of a variety of methodsincluding spraying, intermittent spraying, dipping followed by spraying,spraying followed by dipping, brushing, flowing, printing, spraying,rolling, silk-screening, painting, or immersion, among other methods.

After application of a coating composition to the substrate, it isallowed to coalesce to form a substantially continuous film on thesubstrate. As used herein, “coalescence” refers to the process by whichsolvents are removed prior to curing. During the curing, the polymer maycrosslink with a crosslinker at temperatures ranging from ambienttemperatures to high temperatures. “Ambient temperatures,” for thepurposes of the present invention, include temperatures from about 5° C.to about 40° C. The film thickness may be 10 nm to 3000 microns, such as50 nm to 1000 microns, such as 250 nm to 500 microns, such as 0.25 to150 microns, or 2.5 to 50 microns in thickness. A method of forming acoating film includes applying a coating composition to the surface of asubstrate or article to be coated, coalescing the coating composition toform a substantially continuous film and then curing the thus-obtainedcoating. The curing of these coatings can comprise a flash at ambient orelevated temperatures followed by a thermal bake. Curing can occur atambient temperature of 20° C. to 250° C., for example.

Any of the coatings described herein can include additional materials.Non-limiting examples of additional materials that can be used with thecoating compositions of the present invention include plasticizers,abrasion resistant particles, corrosion resistant particles, corrosioninhibiting additives, fillers including, but not limited to, clays,inorganic minerals, anti-oxidants, hindered amine light stabilizers, UVlight absorbers and stabilizers, surfactants, flow and surface controlagents, thixotropic agents, organic co-solvents, reactive diluents,catalysts, reaction inhibitors, and other customary auxiliaries.

A method of detecting an article may include exposing a surface of anarticle to fluorescence-exciting radiation, the surface being at leastpartially coated with a coating composition comprising: (i) afilm-forming resin, (ii) an IR reflective pigment, and (iii) an IRfluorescent pigment or dye different from the IR reflective pigment. Themethod also includes detecting fluorescence emitted by the coatedsurface in the IR spectrum. The article may be any of the previouslydescribed substrates, such as a portion of an object in a vehicle'ssurroundings. The coating composition may be any of the previouslydescribed coating compositions or the previously described multi-layercoating may coat the article.

By way of example, the previously-described method may be used to detectan article, such as a vehicle (e.g., an automobile). A first vehicle mayinclude a sensor, such as the sensors previously described herein,having a sensitivity in the IR region of the electromagnetic spectrum. Asecond vehicle (or other object in the first vehicle's surroundings) maybe at least partially coated with a coating composition previouslydescribed (including a film-forming resin, an IR reflective pigment, andan IR fluorescent pigment or dye different from the IR reflectivepigment). The sensor on the first vehicle may sense the fluorescenceemitted from the IR fluorescent pigment in the coating composition onthe second vehicle after the IR fluorescent pigment is excited byfluorescence-exciting radiation. Fluorescence-exciting radiation mayinclude radiation produced from headlights or other source on the firstvehicle, and this fluorescence-exciting radiation excites the IRfluorescent pigment or dye in the coating composition on the secondvehicle, causing the IR fluorescent pigment or dye to fluoresce. Thesensor on the first vehicle may sense this fluorescence. Thisinformation detected by the sensor of the first vehicle may then be usedto alert controls of the first vehicle of the proximity of the secondvehicle, allowing the first vehicle to take the appropriate course ofaction, such as braking, accelerating, swerving, or otherwisemaneuvering without human intervention.

The coating composition including the IR reflective pigment and IRfluorescent pigment or dye can function as a marker detectable as anauthentication device, such that the IR fluorescent pigment or dyefluoresces when excited by fluorescence-exciting radiation striking thecoating composition. The other coating layers can be transparent at theemission wavelength and the IR radiation would, thus, “shine through”the other coating layers. In this manner, a predetermined spectralresponse to illuminating radiation from the combined effects of IRreflection and IR fluorescence can be detected. The presence of thepredetermined spectral response may be indicative of the presence of thecoating composition of the present invention, thereby authenticating asubstrate coated therewith.

The coatings of the present application may be used in any coatingdesign for any automotive, aerospace, industrial, and packagingapplications. In particular, the coatings may be used in vehicles, roadmarkings, security elements that can be placed on products, packaging,documents, and articles of manufacture.

The following examples are presented to demonstrate the generalprinciples of the invention. The invention should not be considered aslimited to the specific examples presented. All parts and percentages inthe examples are by weight unless otherwise indicated.

EXAMPLE 1 Synthesis of Red Pigments via Combustion Synthesis andAnalyses

Samples of Al₂O₃ (4 g, 16 g, and 200 g) doped with 1 wt % Cr₂O₃ or 3 wt% of Cr₂O₃ were synthesized via a combustion synthesis method.Analytical testing was conducted on two samples of dark red pigmentsAl₂O₃ doped with 1 wt % Cr₂O₃ and Al₂O₃ doped with 3 wt % of Cr₂O₃.X-ray fluorescence (semi-quantitative) indicated that the elementalcompositions of the pigments were close to their expected values. X-raydiffraction XRD patterns of the two samples showed the presence ofα-Al₂O₃, which is the desired phase of Al₂O₃ for NIR fluorescence. Inaddition, the narrow peaks in the XRD patterns suggested the presence oflarge crystalline particles (FIG. 1 ). Scanning electron microscopy(SEM) was employed to observe the particle size and morphology of thepigment samples prepared by combustion synthesis (FIG. 2 , micrographB). Micrographs indicated the presence of large particles (FIG. 2 ,micrograph A). During the combustion synthesis of the dark red pigments,a green byproduct (γ-alumina) was formed and removed. In addition, thepigments obtained from the combustion synthesis procedure were pink.These pigments become redder as the particle size is increased. Highresolution spectral reflectance measurements showed a sharp absorptiondoublet at fluorescence wavelengths of 692.7 and 694.0 nm.

EXAMPLE 2 Testing Methods

Three calibration panels (whose spectral reflectance values weremeasured using a Perkin Elmer Lamda 900 UV-Vis-NIR spectrometer) wereplaced onto a support along with an experimental sample. The surfacetemperatures were measured with an IR thermometer and plotted versustime. The effective solar absorptance for the experimental sample wasinterpolated from the solar absorptance values for the calibratedsamples. The effective solar reflectance (ESR) was then calculated usingthe formula: ESR=1−effective solar absorptance (a).

FIG. 3 shows a plot of the temperature rise when all of the standardreference samples are used at the same time. These measurements weretaken on a clear summer day, near noon. They show that the sunlittemperature, as a function of spectrometer-measured solar absorptance a,is slightly non-linear. This shows that the basic function oftemperature vs. absorptance a has negative curvature.

Measurement of the fluorescence of the pigments and pigmented coatingswas performed using a NIR spectrofluorometer, which was equipped with anInGaAs detector (capable of measurements from 500-1700 nm). Severalmeasurements were conducted on Cr:Al₂O₃ and Egyptian blue (CaCuSi₄O₁₀)pigments. FIG. 4 shows the fluorescence spectra for 3 wt % Cr₂O₃ dopedAl₂O₃ pigments excited at 500 nm and FIG. 5 shows the fluorescencespectra for Egyptian blue pigments excited at 600 nm.

FIGS. 6A and 6B are graphs showing the fluorescence spectra of coatingsover white substrate pigmented with 500 g/m² of 0 to 4 wt % Cr₂O₃ dopedAl₂O₃. The nominal 0% pigment contains a trace of Cr. The spectra wereobtained with a spectrofluorometer based on a 150 mm Spectralonintegrating sphere and a miniature monochromator with a silicon arraydetector. A monochromator from Ocean Optics (Dunedin, Fla.) was refittedwith a new diffraction grating, a narrower slit and a new silicon arraydetector.

EXAMPLE 3 Coatings Including Red Pigment

Coatings based on PVDF including 500 g/m² of Al₂O₃ doped with Cr₂O₃pigments were synthesized via the combustion process described above(particle size of several microns). These coatings had a reflectance of0.31 at 550 nm. Thinner coatings with 100 g/m² of Al₂O₃ doped with Cr₂O₃synthesized via the combustion process described above had a reflectanceof 0.38 at 550 nm.

Additionally, Al₂O₃ doped with 1.5 wt % and 4.5 wt % Cr₂O₃ pigments withan average particle size of 650 nm were prepared. Egyptian blue pigmentswere also prepared with an average particle size of 650 nm. Thesepigments were included into a coating based on a PVDF film-formingresin. Effective solar reflectance (ESR) measurements were made on thecoatings made using these pigments and are shown in Table 1. Thesubstrates utilized for the evaluation of the coatings were aluminumsubstrates coated with a yellow chrome primer.

TABLE 1 ESR measurements for samples Spectrometer Pigment included (airmass 1, Spectrometer in coating ESR global spectrum) (550 nm) Al₂O₃doped pigment 0.576 0.580 0.57 (1% Cr₂O₃) Al₂O₃ doped pigment 0.5420.554 0.46 (4.5% Cr₂O₃) Egyptian blue 0.470 0.466 0.50

EXAMPLE 4 NIR Spectra of Coatings Including Blue, Purple, Yellow, Orangeand Red Pigments

Alkali earth copper silicate pigments including Egyptian blue(CaCuSi₄O₁₀), Han purple (BaCuSi₂O₆), SrCuSi₄O₁₀, as well as BaCuSi₄O₁₀and SrCuSi₄O₁₀ with lithium and lanthanum as co-dopants, were evaluatedfor NIR fluorescent properties. Egyptian blue (CaCuSi₄O₁₀) emits from900 to 1000 nm. Egyptian blue was incorporated into a coatingformulation based on a PVDF film-forming resin at 0.14 and 0.4 pigmentto binder (P:B) ratios. FIG. 7 shows the fluorescence spectra of (a) anEgyptian blue pigment (bold solid line), (b) a 0.14 P:B Egyptian bluecoating over chrome primed aluminum substrate (light solid line) and (c)a 0.4 P:B Egyptian blue coating over chrome primed aluminum substrate(bold dashed line). The excitation wavelength for all samples was 600nm. FIG. 8 shows the emission spectra of Egyptian blue and Han purple(BaCuSi₂O₆) coatings based on an acrylic paint over a white substrate.

Han blue (BaCuSi₄O₁₀) and the alkali earth metal (SrCuSi₄O₁₀) withlithium and lanthanum as co-dopants showed NIR fluorescent properties.Additionally, cadmium pigments, CdSe and CdTe reagents, a “zirconia” red(a red cadmium pigment coated with a zirconium silicate glass), indigo,blue verditer, copper blue, azurite (Cu₃(CO₃)₂(OH)₂), Ploss blue((CuCa)(CH₃COO)₂·2H₂O), and smalt blue (CoO·K·Si) were prepared. Thesepigments did not show NIR fluorescence during testing, ruling out strongfluorescence but not weak fluorescence. In particular, cadmium pigments(alloys of CdS and CdSe with colors ranging from yellow, to orange, tored, and black) are direct gap semiconductors that do fluoresce (M.Thoury, et al. Appl. Spectroscopy 65, 939-951 (2011)), and nanoparticlesof CdSe have exhibited quantum efficiencies as high as 0.8 (P. Reiss, etal., Nano Letters 2, 781-784 (2002)).

EXAMPLLE 5 Reflectance Measurements of Non-Fluorescent Pigments

FIG. 9 shows a graph of the reflectance of five cadmium pigments,commercially available as artist paints, of formula CdSi_(1-x)Se_(x)with x=0 for yellow to x almost equal to 1 for dark red. As FIG. 9indicates, as x increases, the absorption edge shifts to a longerwavelength. FIG. 10 shows a graph of the reflectance of three cadmiumpigments (dark red, medium red, and light red) and a zirconia redpigment, commercially available from Kremer Pigment Inc. (New York,N.Y.). These reflectance measurements indicate that, even withoutfluorescence, the cadmium pigments are “cool” (IR reflective), with asharp transition from absorptive to reflective at their semiconductingband edges, shown in FIG. 9 and FIG. 10 .

Solar reflectance was tested according to the air-mass 1 globalhorizontal (AM1GH) solar reflectance (SR) test using a standard solarreflectance spectrum that corresponds to a clear day with the sunoverhead (R. Levinson, H. Akbari, and P. Berdahl, “Measuring solarreflectance—part I: defining a metric that accurately predicts solarheat gain,” Solar Energy 84, 1717-1744 (2010)).

FIG. 11 shows a graph of the spectral reflectance of smalt blue(CoO·K·Si), a cobalt potassium silicate glass, as compared to thespectral reflectance of Egyptian blue (CaCuSi₄O₁₀). FIG. 11 shows a verysharp transition from absorptive to reflective right at 700 nm. Thereflectance measurement with respect to Egyptian blue over a whitesubstrate shows some absorption in the 700 to 1100 nm range.

Cadmium yellow, orange, and red pigments were measured for theirfluorescence and they all demonstrated some level of NIR fluorescence.CdSe nanoparticles showed some fluorescence behavior, most notably atabout 850-1300 nm for two cadmium pigments having a deep red color.

EXAMPLE 6 Physical Characterization of Cr₂O₃ Doped Al₂O₃Pigments

Two samples of Cr₂O₃ doped Al₂O₃ with different particle sizes andlevels of chromium (1.5 wt % Cr₂O₃ and the other was 4.5 wt % Cr₂O₃)were analytically tested (microscopy, particle size, and elementalcomposition). The two pigments contained different levels of chromium asevidenced by the elemental data (x-ray fluorescence). The two pigmentswere evaluated for their NIR fluorescence behavior, which indicated thatthe 1.5 wt % Cr₂O₃ doped Al₂O₃ displayed a more intense fluorescencethan the 4.5 wt % Cr₂O₃ doped Al₂O₃.

FIG. 2 shows scanning electron micrographs of the 1% Cr₂O₃ doped Al₂O₃pigment (Micrograph A) and the 3% Cr₂O₃ doped Al₂O₃(Micrograph B). Theparticle size for the 3% Cr₂O₃ doped Al₂O₃ pigment was much smaller (650nm) than the 1% Cr₂O₃ doped Al₂O₃ (several microns).

EXAMPLE 7 Spectroscopy Data for Alkali Earth Copper Silicate Pigments inDifferent Types of Coatings

Table 2 lists alkali earth copper silicate pigments that were tested forNIR fluorescence.

TABLE 2 Alkali earth copper silicate pigments Chemical formula Commonname BaCuSi₂O₆ Han purple CaCuSi₄O₁₀ Egyptian blue SrCuSi₄O₁₀ —BaCuSi₄O₁₀ Han blue Sr(La,Li)CuSi₄O₁₀ — Ba(La,Li)CuSi₄O₁₀ —

FIG. 12 shows the NIR fluorescence spectra of several alkali earthcopper silicate pigments (excitation wavelength of 600 nm). Ruby (1.5 wt% Cr₂O₃ doped Al₂O₃) was included for comparison (excitation wavelengthof 550 nm). Ba(La,Li)CuSi₄O₁₀ and Sr(La,Li)CuSi₄O₁₀ NIR fluorescencespectra were measured for small and large particle sizes.

Four coatings based on two pigments Ba(La,Li)CuSi₄O₁₀ (small particles)and SrCuSi₄O₁₀ (large particles) in two film-forming resins (onecontaining PVDF and the other being acrylic-based) were evaluated. Table3 shows the solar reflectance (AM1GH and ESR), benefit fromfluorescence, reflectance, and substrate of these four coatings in afilm-forming resin containing PVDF over a yellow substrate and a whitesubstrate. Benefit from fluorescence is the difference between AM1GH andESR solar reflectance, indicating the contribution of fluorescence tothe solar reflectance. Table 4 shows the solar reflectance (AM1GH andESR), benefit from fluorescence, reflectance, and substrate of thesefour coatings in an acrylic film-forming resin over a white substrate.

TABLE 3 Spectroscopy data for Ba(La,Li)CuSi₄O₁₀ (small particles) andSrCuSi₄O₁₀ (large particles) in a film-forming resin containing PVDFSolar Solar Benefit Pigment in reflectance reflectance from ReflectancePVDF coating (AM1GH)¹ (ESR)² fluorescence (550 nm)³ SubstrateBa(La,Li)CuSi₄O₁₀ 0.442 0.447 0.005 0.365 Yellow⁴ (small particles)Ba(La,Li)CuSi₄O₁₀ 0.573 0.621 0.048 0.485 White⁵ (small particles)SrCuSi₄O₁₀ 0.434 0.446 0.012 0.349 Yellow⁴ (large particles) SrCuSi₄O₁₀0.605 0.649 0.044 0.510 White⁵ (large particles) ¹AM1GH refers to thesolar spectrum used to tabulate the solar reflectance from thespectrometer data. ²The ESR (Effective Solar Reflectance) is obtainedfrom temperature measurements in sunlight. ³The reflectance at 550 nm isa measure of visual brightness. ⁴Yellow chrome primer over aluminumsubstrate. Appearance is green with a blue overcoat. ⁵White primer overyellow chrome primed aluminum substrate.

TABLE 4 Spectroscopy data for Ba(La,Li)CuSi₄O₁₀ (small particles) andSrCuSi₄O₁₀ (large particles) in an acrylic film-forming resin containingSolar Solar Benefit Pigment Pigment in acrylic- reflectance reflectancefrom Reflectance amount based coating (AM1GH)¹ (ESR)² fluorescence (550nm)³ Substrate (g/m2)⁴ Ba(La,Li)CuSi₄O₁₀ 0.361 0.436 0.075 0.192 Bright160 (small particles) white SrCuSi₄O₁₀ (large 0.405 0.498 0.093 0.173Bright 100 particles) white ¹AM1GH refers to the solar spectrum used totabulate the solar reflectance from the spectrometer data. ²The ESR(Effective Solar Reflectance) is obtained from temperature measurementsin sunlight. ³The reflectance at 550 nm is a measure of visualbrightness. ⁴Amount of pigment per unit area

FIG. 13 shows the plots of spectral reflectance for PVDF-type coatingscontaining Ba(La,Li)CuSi₄O₁₀ (small particles) and SrCuSi₄O₁₀ (largeparticles) over white and yellow substrates. FIG. 14 shows the plots ofspectral reflectance for acrylic-based coatings containingBa(La,Li)CuSi₄O₁₀ (small particles) and SrCuSi₄O₁₀ (large particles)over white substrates. FIG. 15 shows the reflectance of the yellowprimer and the white-coated substrates used in the coatings of FIGS. 13and 14 .

FIG. 16A shows the fluorescence from several samples includingSrCuSi₄O₁₀ (large particle size) as compared to Egyptian blue. The twotop curves (SrCuSi₄O₁₀ (Large) (100 g/m²) over white and SrCuSi₄O₁₀(Large) (50 g/m²) over white) show that increased pigment amount yieldsmore fluorescence. FIG. 16B shows the fluorescence for samples includingBa(La,Li)CuSi₄O₁₀ (small). FIG. 16C shows the reflectance data thatcorresponds to FIGS. 16A and 16B. FIG. 16D shows the fluorescence of astrontium compound doped with equal amounts of La and Li, compared withan undoped material. FIG. 16E shows the reflectance data correspondingto FIG. 16D. FIG. 16F shows the fluorescence data on a BaCuSi₄O₁₀ samplethat is contaminated with CuO. FIG. 16G shows the reflectance datacorresponding to the fluorescence plot of FIG. 16F. The spectra in thevisible region show that before washing, the color is gray, and afterwashing the color is blue. FIG. 16H shows the fluorescence of someEgyptian blue samples. 16I shows the reflectance data corresponding toFIG. 16H.

EXAMPLE 8 Ratios of Pigment to Film-Forming Resin and Film Thickness

The effect of pigment loading level and the effect of film thickness (ata given pigment to binder (P:B) ratio) on fluorescence intensity wereevaluated. A pigment to binder ladder ranging from 0.2 P:B to 0.8 P:Band film thickness ladders for each P:B ratio ranging from one to threecoats were coated over an aluminum substrate coated with a yellow chromeprimer and a white primer. 3% Cr₂O₃ doped Al₂O₃ pigment (small particles650 nm) was incorporated into a PVDF-based coating system during thedispersion phase of paint making. The color of the coatings was pink.Test coatings were prepared over yellow chrome primed substrates. FIG.17 shows nine fluorescence spectra corresponding to coatings with threeP:B ratios (0.2, 0.4, and 0.8) and three film thicknesses (1 coat, 2coats, 3 coats) for each coating. The intensity of the fluorescenceincreases with increasing P:B ratio and film thickness.

These coatings and additional coatings (3% Cr₂O₃ doped Al₂O₃ coatingsover yellow primer, Egyptian blue, Han blue and Han purple) were alsoevaluated for ESR measurements in the sun. ESR may also be expressed interms of the effective solar absorptance, a according to the followingequation a=1−ESR. FIG. 18 shows the temperature measurements for 18samples (1.5% Cr₂O₃ doped Al₂O₃ pigment with P:B ratios of 0.2, 0.4, and0.8 and 1, 2, and 3 coats film thickness, 1.5% Cr₂O₃ doped Al₂O₃coatings over yellow primer, Egyptian blue pigment with P:B ratios of0.4 and 0.8; Han blue pigment with P:B ratios of 0.4 and 0.8; Han purplepigment with P:B ratios of 0.4 and 0.8), and also for 4 gray-scalestandards. The resulting values are plotted versus the a-values fromspectrometer spectral reflectance measurements. Linear least square fitlines are given for the calibration samples (bold line), and for thetested samples. The two lines are parallel, but are shifted from oneanother by about 0.5° C. FIG. 18 shows the temperature differences abovethe ambient temperature for these 18 samples and the 4 calibratedstandards. The ESR values are obtained by using the sample temperaturesto determine the solar absorption the calibration samples would requireto come to the same temperature. From the cluster of coolest samples,the difference in temperatures is about 2.5° C., which may be due to thea-values of the samples and/or due to fluorescence. It is estimated thatabout 0.8° C. is due to a-values, and 1.7° C. is due to fluorescence.Using the slope of the curve, a contribution of roughly 0.04 to the a(and ESR) comes from fluorescence.

To assign temperature-based ESR values to the samples (Table 5), thebold calibration line and the observed temperatures were used. Inearlier measurements of effective absorptance a, values on the order of0.2 were measured. Then, an accuracy of 0.01-0.02 was achieved, about 5to 10% of the value. In the current measurements with larger values ofa, errors as large as about 0.04 may be present.

The data in FIG. 18 cluster into three groups. The lowest temperaturegroup is associated with the ruby pigmented coatings over a whiteprimer. The three samples near 23° C. temperature rise were rubypigmented over a yellow primer, and the warmest group contained thecoatings with copper silicate pigments (Egyptian blue, Han blue, and Hanpurple) over a yellow primer. Within the lowest temperature group, thereis a correlation of temperature with fluorescence intensity. Forexample, the two lowest data points at 16.5° C. and 16.6° C. bothexhibited bright fluorescence (Table 5).

TABLE 5 Solar reflectance (SR) and Effective Solar Reflectance (ESR)data for NIR fluorescent pigments PVDF-based coatings (Reflectance at550 nm, measured with filter to exclude fluorescence) Temp. rise in SRfrom the sun, spectrometer ESR relative Film (corrected to from to airFluorescence P:B Thickness omit ruby temp. temp. brightness, VisualPigment ratio (mils) fluorescence) meas. (K) peak height brightness ruby0.2 0.94 0.682 0.648 18.8 11 0.703 ruby 0.2 2.71 0.679 0.672 17.8 220.658 ruby 0.2 3.05 0.67 0.665 18.1 27 0.624 ruby 0.4 0.87 0.686 0.67217.8 20 0.664 ruby 0.4 2.65 0.691 0.702 16.6 37 0.603 ruby 0.4 3.030.679 0.665 18.1 36 0.583 ruby 0.8 0.78 0.691 0.658 18.4 27 0.636 ruby0.8 1.76 0.703 0.685 17.3 41 0.573 ruby 0.8 2.49 0.688 0.704 16.5 390.542 Egyptian 0.4 0.73 0.396 0.375 29.9 0.22 0.353 blue Egyptian 0.80.81 0.402 0.412 28.4 0.22 0.363 blue Han blue 0.4 0.81 0.345 0.35 30.90.12 0.212 Han blue 0.8 0.89 0.281 0.266 34.3 0.12 0.116 Han 0.4 N/A0.393 0.365 30.3 0.11 0.201 purple Han 0.8 0.89 0.351 0.348 31 0.110.124 purple

Table 6 shows the temperature rise measurements using calibrated graysamples.

TABLE 6 Temperature rise measurements using calibrated gray samplesSpectrometer Temperature absorptance rise in (1-SR) the sun (K.) 0.26715.5 +− 0.5 0.311 16.6 +− 0.3 0.506 26.0 +− 0.6 0.622 29.2 +− 0.6

Similar to the P:B ladder and film thickness study conducted with theruby pigment, a P:B ladder and film thickness study was conducted withan alkali earth copper silicate pigment (Sr (La,Li)CuSi₄O₁₀). Thispigment was incorporated into a PVDF-based coating system at P:B ratiosof 0.2, 0.4 and 0.8 and these coatings were applied over aluminumsubstrates coated with a yellow chrome primer and white primer. Threefilm thicknesses were applied for each P:B coating, namely 0.8 mils, 1.6mils and 2.4 mils. FIG. 19 shows the NIR fluorescence intensityincreased with increasing P:B ratio (i.e. increased pigment loading). Inaddition, NIR fluorescence intensity increased with increasing filmthickness for the 0.2 and 0.4 P:B coatings. For the 0.8 P:B coating, the1.6 mil thick film demonstrated more intense fluorescence than the 2.7mil thick film.

FIG. 20 shows the peak heights of the fluorescence of the coatings ofFIG. 19 as a function of the product of P:B ratio and coating thickness,that is, of pigment amount. As the pigment amount is increased, the peakheight smoothly increases from zero and bends over as additionalincrements of pigment contribute less to the fluorescence.

EXAMPLE 9 Co-Pigments Using Two NIR Fluorescent Pigments

Coating formulations were prepared using two scaled-up NIR fluorescentpigments. Two NIR fluorescent pigments (ruby and Han Blue) wereformulated into two PVDF-based coatings. The first coating was darkbrown as ruby was incorporated into this formula at weight percentagesranging from 14% to 43% (FIG. 21A). The second coating was black as HanBlue was formulated into this coating from 51% to 86% by weight (FIG. 21B). ESR measurements were conducted on these coatings. Measurements weremade on a control brown PVDF-based coating reference sample, and on asample which contained 43% ruby pigment. Spectrometer measurementsindicated that the solar reflectance values were 0.264 and 0.331,respectively. Fluorescence measurements on the ruby sample did showcharacteristic ruby fluorescence, but the amount was one or two ordersof magnitude lower than ruby without other pigments. The ESRmeasurements yielded 0.256 and 0.325, both values deviating from thespectrometer measurements by less than 0.010.

SrCuSi₄O₁₀ (large particles) was mixed with yellow (an organic yellowpigment, Liquitex “azo” yellow-orange (Diarylide yellow, PY83 HR70), anda mixed metal oxide, Shepherd 193) to make NIR fluorescent greencoatings. FIG. 22 shows coatings including Sr(La,Li)CuSi₄O₁₀ (Top),Sr(La,Li)CuSi₄O₁₀ with azo yellow (Bottom left) and Sr(La,Li)CuSi₄O₁₀with with Shepherd yellow 193 (Bottom right). In both cases fluorescencewas similar to that of the blue alone (Table 7). FIG. 23 shows aphotograph of the blue-shade black sample made with a SrCuSi₄O₁₀ (large)pigmented acrylic coating over orange over a bright white substrate. Theorange was a Liquitex cadmium light red hue (imitation) with one brushedcoating, which had an ESR of 0.451. The spectrometer reflectance was0.14 in the blue at 450 nm, 0.07 in the center of the visible (green) at550 nm and 0.10 in the red at 650 nm. Thus this sample was nearly black.

TABLE 7 Solar reflectance and effective solar reflectance data for‘green’ coatings prepared using different yellow pigments along withBlue 4—Lot 2 Blue Solar Solar pigment Pigments in reflectancereflectance Benefit from Reflectance amount coatings (AM1GH) (ESR)fluorescence (550 nm) Substrate (g/m²)⁸ #193 0.382 0.486 0.104 0.24Bright 90 yellow⁶ white (buff) + Sr(La,Li)Cu Si₄O₁₀ Azo yellow⁷ + 0.3380.479 0.141 0.26 Bright 130 Sr(La,Li)Cu white Si₄O₁₀ Sr(La,Li)Cu 0.4050.498 0.093 0.173 Bright 100 Si₄O₁₀ white ⁶Available from The ShepardColor Company (Cincinnati, OH). ⁷Diarylide yellow, PY83 HR70. ⁸Amount ofpigment per unit area.

EXAMPLE 10 Co-Pigments Using NIR Fluorescent Pigments and IR ReflectivePigments

A control mocha PPG Duranar® coil coating was prepared by blending PPGDuranar® clear, IR reflective black, flatting slurry, red, white andyellow tint pastes to achieve the desired color.

An experimental mocha PPG Duranar® coil coating was prepared using NIRfluorescent pigments and IR reflective pigments. A blue tint pastecomprising NIR fluorescent Han blue and an orange tint paste comprisingIR reflective Orange 10C341 were prepared in a Duranar® formula. Theblue and orange tint pastes were mixed to attain the same color as thecontrol mocha coating. The experimental mocha coating and control mochacoating are shown side-by-side in FIG. 24 .

The substrates used for this evaluation were chrome primed aluminumsubstrates, which were coated with a white PPG Duranar® coating. Theexperimental and control mocha Duranar® coatings were coated onto thesubstrates and cured at 480° F. for 30 seconds to reach a final filmthicknesses of 74 micrometers.

NIR fluorescence measurements conducted on coated substrates shown inFIG. 24 indicated that the experimental mocha coating containing NIRfluorescent Han blue and IR reflective orange displayed NIR fluorescence(when excited at 600 nm), while the control mocha coating containingonly IR reflective pigments did not exhibit any fluorescence (whenexcited at 600 nm) (FIG. 25 ).

The dashed curve of FIG. 25 is for the experimental mocha coatingcontaining NIR fluorescent pigment and IR reflective pigment. The solidcurve of FIG. 25 is for the control mocha coating containing IRreflective pigment. The excitation wavelength was 600 nm. The emissionmeasurement range was from 650 nm to 1700 nm. NIR fluorescencemeasurements were conducted with a PTI QM-500 QuantaMaster™ NIRspectrofluorometer equipped with an InGaAs detector.

To determine the cooling benefit of the experimental mocha coating, boththe control mocha coating and the experimental mocha coating were placedunder heat lamps for the same amount of time. The surfaces of the coatedsubstrates were monitored over a 10-minute period. The experimentalmocha coating, which contained both NIR fluorescent Han blue and IRreflective orange was consistently 10 degrees cooler than the coatingfrom the control mocha coating, which contained IR reflective black.Upon reaching equilibrium, the temperature of the coating surface of theexperimental mocha coating was 160° F., while the temperature of thecontrol mocha coating surface was 170° F.

EXAMPLE 11 Accelerated Testing, Outdoor Exposure and ThermalMeasurements

In addition to conducting weathering studies, thermal measurements wereconducted by using a portable field testing station to evaluate theperformance of coatings containing NIR fluorescent pigments. Theportable field testing station is equipped with a pyranometer,anemometer, wind vane, and thermocouples (samples are on R4 foaminsulation). The DataTaker™ 500 is capable of measuring up to eightsamples (3″×3″) along with an ambient sensor.

Thermal measurements, were conducted on a series of coated substratesusing the field station. The brown coatings evaluated contained varyinglevels of ruby pigment (14-43% by weight) and a brown co-pigment. WhileESR measurements were not conducted, temperature measurements of thepanels were made (FIG. 26 ). The coatings with ruby pigment levels morethan 30% by weight were about 4-5° C. cooler than coatings containingless than 30% ruby pigment.

The present invention further includes the subject matter of thefollowing clauses.

Clause 1: a coating composition comprising: (i) a film-forming resin;(ii) an infrared reflective pigment; and (iii) an infrared fluorescentpigment or dye different from the infrared reflective pigment.

Clause 2: The coating composition of clause 1, wherein the coatingcomposition, when cured to form a coating and exposed to radiationcomprising fluorescence-exciting radiation, emits fluorescence in theinfrared spectrum at a greater intensity compared to the same coatingexposed to the radiation comprising fluorescence-exciting radiationexcept without the infrared fluorescent pigment or dye.

Clause 3: The coating composition of clause 1 or 2, wherein the coatingcomposition, when cured to form a coating and exposed to radiationcomprising fluorescence-exciting radiation, emits fluorescence in theinfrared spectrum at least twice the intensity compared to the samecoating exposed to the radiation comprising fluorescence-excitingradiation except without the infrared fluorescent pigment or dye.

Clause 4: The coating composition of clause 2 or 3, wherein thefluorescence emitted by the infrared fluorescent pigment is detectableby a sensor.

Clause 5: The coating composition of clause 4, wherein the sensor hassensitivity in the infrared region of the electromagnetic spectrum.

Clause 6: The coating composition of any of clauses 1 to 5, wherein thecoating composition is substantially free of an infrared absorbingcomponent.

Clause 7: The coating composition of any of clauses 2 to 6, wherein theradiation comprising fluorescence-exciting radiation is produced fromsunlight, incandescent light, fluorescent light, xenon light, laser, LEDlight, or a combination thereof.

Clause 8: The coating composition of any of clauses 1 to 7, furthercomprising a colorant.

Clause 9: The coating composition of any of clauses 1 to 8, wherein theinfrared reflective pigment reflects at a first wavelength and theinfrared fluorescent pigment or dye fluoresces at a second wavelength,and wherein a balance of the coating composition is transparent at thefirst wavelength and second wavelength.

Clause 10: The coating composition of any of clauses 1 to 9, wherein theinfrared fluorescent pigment comprises Han purple, Han blue, Egyptianblue, ruby, cadmium pigment, CdSe and CdTe compounds, zirconia red,indigo, blue verditer, copper blue, azurite, ploss blue, smalt, or acombination thereof.

Clause 11: The coating composition of any of clauses 1 to 10, whereinthe infrared fluorescent pigment or dye comprises an organic pigment ordye.

Clause 12: A multi-layer coating comprising: (i) a first coating layercomprising a cured infrared reflective coating composition; and (ii) asecond coating layer overlying at least a portion of the first coatinglayer, the second coating layer comprising a cured coating compositionaccording to any of clauses 1 to 11.

Clause 13: A substrate at least partially coated with the material ofany of clauses 1 to 12.

Clause 14: The substrate of clause 13, wherein the substrate comprisesat least a portion of an object in a vehicle's surroundings.

Clause 15: A method of detecting an article comprising: (a) exposing asurface of an article to radiation comprising fluorescence-excitingradiation, the surface being at least partially coated with a coatingcomposition comprising: (i) a film-forming resin, (ii) an infraredreflective pigment, and (iii) an infrared fluorescent pigment or dyedifferent from the infrared reflective pigment; and (b) detectingfluorescence emitted by the coated surface in the infrared spectrum.

Clause 16: The method of clause 15, wherein the coating composition,when cured to form a coating and exposed to the radiation comprisingfluorescence-exciting radiation, emits fluorescence in the infraredspectrum at a greater intensity compared to the same coating exposed tothe radiation comprising fluorescence-exciting radiation except withoutthe infrared fluorescent pigment or dye.

Clause 17: The method of clause 15 or 16, wherein the fluorescence isdetected by a sensor having sensitivity in the infrared region of theelectromagnetic spectrum.

Clause 18: The method of any of clauses 15 to 17, wherein the radiationcomprising fluorescence-exciting radiation is produced from sunlight,incandescent light, fluorescent light, xenon light, laser, LED light, ora combination thereof.

Clause 19: The method of any of clauses 15 to 18, wherein the articlecomprises at least a portion of an object in a vehicle's surroundings.

Clause 20: The method of clause 19, wherein the fluorescence is detectedby a sensor on the vehicle.

Clause 21: The coating composition of any of clauses 1 to 11, whereinthe infrared fluorescent pigment comprises SrCuSi₄O₁₀, Sr(La,Li)CuSi₄O₁₀, Ba(La, Li)CuSi₄O₁₀, or a combination thereof.

Clause 22: The coating composition of any of clauses 1 to 11, furthercomprising an infrared transparent pigment.

Clause 23: The coating composition of any of clauses 1 to 11, whereinthe infrared fluorescent pigment fluoresces in the near-infrared regionof the electromagnetic spectrum when excited by radiation comprisingfluorescence-exciting radiation.

Whereas particular features of this invention have been described abovefor purposes of illustration, it will be evident to those skilled in theart that numerous variations of the details of the present invention maybe made without departing from the invention.

The invention claimed is:
 1. A method of detecting an object in a pathof an autonomous vehicle, comprising: directing infrared electromagneticradiation from a radiation source mounted on an autonomous vehicle at anobject at least partially coated with a coating composition comprising:(i) a film-forming resin, (ii) an infrared reflective pigment, and (iii)an infrared fluorescent pigment or dye different from the infraredfluorescent pigment; and detecting, by a radiation sensor mounted on theautonomous vehicle, reflected and fluoresced radiation emitted by theinfrared reflective pigment and the infrared fluorescent pigment inresponse to excitation by incident radiation from the infraredelectromagnetic radiation.
 2. The method of claim 1, further comprising:in response to detecting the reflected and fluoresced radiation,determining a proximity of the autonomous vehicle to the coated object.3. The method of claim 2, further comprising: in response to determiningthe proximity of the autonomous vehicle to the coated object, causingthe autonomous vehicle to react without human intervention by at leastone of braking, accelerating, or swerving.
 4. The method of claim 1,wherein the coated object is a second vehicle, a road, a road barrier,signage, and/or an object in a path of the autonomous vehicle.
 5. Themethod of claim 1, wherein the infrared fluorescent pigment or dyeabsorbs incident electromagnetic radiation from the radiation source ata first wavelength and fluoresces electromagnetic radiation at a secondwavelength when excited by the incident electromagnetic radiation fromthe radiation source at the first wavelength.
 6. The method of claim 5,wherein the second wavelength corresponds to a lower energy wavelengthcompared to the first wavelength.
 7. The method of claim 5, wherein thesecond wavelength is in the near-infrared region of from 700 nm to 2500nm.
 8. The method of claim 1, wherein the infrared reflective pigmentreflects incident electromagnetic radiation from the radiation source ata first wavelength, wherein the first wavelength is in the near-infraredregion of from 700 nm to 2500 nm.
 9. The method of claim 1, wherein theinfrared reflective pigment reflects at a first wavelength and theinfrared fluorescent pigment or dye fluoresces at a second wavelength.10. The method of claim 9, wherein a balance of the coating compositionis transparent at the first and second wavelengths.
 11. An autonomousvehicle guidance system, comprising: an autonomous vehicle; a radiationsource mounted on the autonomous vehicle, the radiation source directinginfrared electromagnetic radiation at an object at least partiallycoated with a coating composition comprising: (i) a film-forming resin,(ii) an infrared reflective pigment, and (iii) an infrared fluorescentpigment or dye different from the infrared fluorescent pigment; and aradiation sensor mounted on the autonomous vehicle detecting reflectedand fluoresced radiation emitted by the infrared reflective pigment andthe infrared fluorescent pigment in response to excitation by incidentradiation from the infrared electromagnetic radiation.
 12. Theautonomous vehicle guidance system of claim 11, wherein the autonomousvehicle is configured to determine a proximity of the autonomous vehicleto the coated object in response to detecting the reflected andfluoresced radiation.
 13. The autonomous vehicle guidance system ofclaim 12, wherein the autonomous vehicle is configured to react withouthuman intervention by at least one of braking, accelerating, or swervingin response to determining the proximity of the autonomous vehicle tothe coated object.
 14. The autonomous vehicle guidance system of claim11, wherein the coated object is a second vehicle, a road, a roadbarrier, signage, and/or an object in a path of the autonomous vehicle.15. The autonomous vehicle guidance system of claim 11, wherein theinfrared fluorescent pigment or dye absorbs incident electromagneticradiation from the radiation source at a first wavelength and fluoresceselectromagnetic radiation at a second wavelength when excited by theincident electromagnetic radiation from the radiation source at thefirst wavelength.
 16. The autonomous vehicle guidance system of claim15, wherein the second wavelength corresponds to a lower energywavelength compared to the first wavelength.
 17. The autonomous vehicleguidance system of claim 15, wherein the second wavelength is in thenear-infrared region of from 700 nm to 2500 nm.
 18. The autonomousguidance vehicle system of claim 11, wherein the infrared reflectivepigment reflects incident electromagnetic radiation from the radiationsource at a first wavelength, wherein the first wavelength is in thenear-infrared region of from 700 nm to 2500 nm.
 19. The autonomousvehicle guidance system of claim 11, wherein the infrared reflectivepigment reflects at a first wavelength and the infrared fluorescentpigment or dye fluoresces at a second wavelength.
 20. A coated object ina path of an autonomous vehicle, comprising: an object in a path of anautonomous vehicle and at least partially coated with a coatingcomposition comprising: (i) a film-forming resin, (ii) an infraredreflective pigment, and (iii) an infrared fluorescent pigment or dyedifferent from the infrared fluorescent pigment, wherein the coatedobject is contacted with infrared electromagnetic radiation directedfrom a radiation source mounted on the autonomous vehicle, wherein theinfrared reflective pigment and the infrared fluorescent pigment or dyereflect and fluoresce, respectively, at least a portion of the infraredelectromagnetic radiation directed from the radiation source in adirection of a radiation detector mounted on the autonomous vehicle.